A scroll type fluid machine is used as a scroll type compressor, a scroll type vacuum pump, a scroll type expander, a scroll type air blower, and the like. A scroll type fluid machine is constituted by a fixed scroll and an orbiting scroll having spiral wrap portions that stand upright on endplates thereof, and a driving mechanism that causes the orbiting scroll to orbit without rotating. A plurality of enclosed spaces surrounded by the end plates and the wraps of the fixed scroll and the orbiting scroll are formed, and a processing subject gas is introduced into the enclosed spaces and subjected to processing such as compression, expansion, or decompression.
To secure a compression performance, a decompression performance, or the like in a scroll type fluid machine, the enclosed spaces formed by the fixed scroll and the orbiting scroll must be sealed tightly so that compression and decompression can be performed on the gas suctioned therein. Further, to suppress galling, wear, damage, and the like between the wrap portions of the fixed scroll and the orbiting scroll, a minute gap of a size at the micron scale must be formed between the wrap portion of the fixed scroll and the wrap portion of the orbiting scroll. In consideration of these points, a high degree of processing precision is required to form the fixed scroll and the orbiting scroll.
However, the fixed scroll and the orbiting scroll are constantly heated and cooled by the gas that is compressed or decompressed in the enclosed spaces, and therefore undergo constant thermal deformation. Moreover, the gas has different temperatures in a central region and an outside region of the scrolls, and therefore thermal strain occurs due to a resulting temperature difference. Scrolls in which thermal strain has occurred are shown in FIG. 3 of Patent Document 2, to be described below.
FIG. 3 of Patent Document 2 is shown in FIG. 5. In FIG. 5, a fixed scroll 100 is constituted by an end plate 102 and a wrap portion 104, while an orbiting scroll 110 is constituted by an end plate 112 and a wrap portion 114. In a scroll type compressor, a temperature and a pressure are low in an outer peripheral portion and increase steadily toward a central portion. Therefore, stress acts on the wrap portion 114 of the orbiting scroll 110 from the central portion toward the outer peripheral portion, causing the wrap portion 114 to deform in the manner of an opening petal. This tendency is also observed in the fixed scroll 100, albeit to a lesser degree. As a result, gaps 120a and 120b between the wrap portions 104, 114 and the end plates 102, 112 increase from the central portion toward the outer peripheral portion.
However, managing a scroll type compressor to ensure that both the enclosed spaces are tightly sealed and the minute gap is secured between the wrap portions is not easy. One method of securing the minute gap between the wrap portions is to apply a coating to a side face or an end face of the wrap. An optimum gap is formed between the wrap portions by interposing a coating film having a lubricating property and a wear-resistant property between the wrap portions, providing the coating film with a buffer function, and scraping away a surplus part of the coating film during an operation.
Patent Document 1 discloses a configuration in which an elastic coating layer constituted by an elastic material such as rubber or a synthetic resin material is formed on a side face of at least one wrap portion of a scroll, and a lubricating coating layer constituted by a self-lubricating material such as a resin material containing molybdenum disulfide (MoS2), a fluorine-based resin material, or a carbon-based resin material is formed on the elastic coating layer.
Patent Document 2 relates to a scroll type pump, and discloses a configuration and a method for applying a surface coating formed from a coolant-resistant resin containing MoS2 particles to a wrap portion and an end plate of a scroll. In the coating method, the scroll type pump is assembled and operated after applying the surface coating but before the surface coating hardens, whereby surplus surface coating is discharged to the exterior of the scroll such that the surface coating obtains an appropriate coating thickness.
Patent Document 3 discloses a configuration for forming a lubricating coating layer constituted by a similar self-lubricating material to that of Patent Document 1 on a side face of a wrap portion of a scroll.
Patent Document 1: Japanese Patent Application Publication No. H11-280669
Patent Document 2: Japanese Patent Application Publication No. 2003-35284
Patent Document 3: Japanese Patent Application Publication No. 2009-57897